1. Technical Field
The present disclosure relates to a sieve device, a powder transporting unit including the sieve device, an image forming apparatus including the powder transporting unit, and a method of transporting powder.
2. Description of Related Art
Powder pumps, such as screw pump, bellows pump, diaphragm pump, are widely used in various fields. These powder pumps transport powder with a high degree of accuracy. Image forming apparatuses, such as copiers, are generally equipped with a screw pump that transports toner particles (i.e., powder) from a toner cartridge to a developing device. Toner particles generally receive mechanical pressure from the screw pump during the transportation and therefore get aggregated to undesirably produce coarse particles.
JP-2002-287497-A describes a developer transporting device equipped with a mesh. In this device, coarse particles are not allowed to pass through the mesh. Therefore, the device is capable of transporting toner particles without coarse particles. However, merely providing the mesh is insufficient in terms of efficiency of removal of coarse particles.
JP-2006-23782-A describes a method of removing coarse particles from toner by means of sieving. In this method, coarse particles are removed by sieving toner with a filter vibrated by ultrasonic waves. However, there is a concern that the apertures of the filter are clogged with toner particles softened by frictional heat generated due to vibration of the filter, or another concern that the apertures of the filter are enlarged by stress caused by vibration of the filter.
JP-2009-90167-A describes a sieve device having a rotation shaft, a cylindrical sieve disposed coaxially with the rotation shaft, and rotary blades attached to the rotation shaft. Further, this sieve device has a mechanism of transporting powder from inside to outside of the cylindrical sieve. Thus, the powder is sieved only by rotating the rotary blades without vibrating the sieve.
The mechanism of transporting powder from inside to outside of the cylindrical sieve requires a large space for collecting powders passed through the sieve. Therefore, this sieve device and an image forming apparatus equipped therewith get undesirably large in size.